1. Field of the Invention
The present invention relates to an input device, and more particularly, to a key scan type input device that can prevent a key input error due to the defect of components thereof.
2. Description of the Related Art
A cooking device is one of typical home appliances. The cooling device includes an electric oven, an electronic range, an electric range, a gas range, and a gas oven range. Although, the concept of the present invention is not limited to the cooking device, the cooking device will be used to describe the concept of the present invention.
Recently, a key scan type input device or a touch type input device has been used to manipulate an operation (on/off operation or mode setting operation) of the home appliances instead of using a physical structure such as a switch or a knob.
A typical key scan type input device includes a key matrix on which a plurality of keys for controlling the system are arranged in a matrix pattern and a microcomputer applying a scan signal to the key matrix and determining a key signal output from the key matrix in a scan signal section.
That is, the keys include a power on/off key (STOP/Clear), on/off keys (LF ON-OFF, RF ON-OFF, LR ON-FF, RR ON-OFF, CR ON-OFF). A variety of number keys for the start, timer, cooking time, start time, bake, broil, oven light, cool/warm, and power level are constituted in the single key matrix.
Each column of the key matrix is connected to a corresponding output port and each line of the key matrix is connected to a corresponding input port of the microcomputer.
With the above-described structure, the microcomputer sequentially outputs scan signals (pulse signals) with respect to the respective columns of the key matrix through the output ports. When the user inputs a specific key, the microcomputer determines the input signal of the relevant key by receiving the key signal output from the key matrix through the input port in the scan signal section.
For example, when the user inputs a open/clear key on the key matrix, a key signal having a low level I input through the relevant input port at a timing point where the scan signal is output from the output port of the microcomputer so that the microcomputer can recognize the open/clear.
Therefore, the key scan input device is designed to read the key contacted by the user by applying a scan signal (pulse signal) to each column of the key matrix on which all of the key are arranged.
However, problems of the typical key input device are that the key signal output is normally realized when there is a process or property error in the circuit components or the circuit components are damage, or a short circuit or opening occurs between the circuit components, and thus the information input by the user through the key cannot be accurately read. Particularly, when the keys related to the on/off of the power or load (heater) are damaged, the power cannot be turned off or the operation of the load cannot be stopped. This may cause the fire or the damage of the whole system.
Furthermore, when the user touches the off key but the system is not turned off due to the malfunction of the off key, the user may think that the system is turned off and thus open the door. In this case, since the internal heat of the system may be applied to the user, the user may be injured due to the heat.